Conducting polymers are polymers typically having a conductivity of 10−7 Scm−1 (higher than that of semiconductors) or higher. In most cases, a high conductivity can be obtained by doping an electron acceptor or an electron donor into a polymer. Doped polyethylene, polypyrrole, and polythiopene are representative examples of conducting polymers.
Polyanilline, polypyroole, and polythiopene as conducting polymers have attracted a lot of attention since they can be easily polymerized and have relatively high electrical conductivities and excellent properties such as oxidation stability and the like. These high-molecular compounds exhibit a corrosion resistance and an electrochromic characteristic in addition to an electrical conductivity. Further, they have been widely applied to electronic devices such as semiconductors since they have merits of being light and easily processable as properties of polymers.
Polyacetylene is the first-discovered conducting polymer. It is just a semiconductor, but when processed with iodine, it has an electrical conductivity which is substantially equivalent to that of a metal. The research on conducting polymers has begun after the discovery of an insulator-metal phase transition phenomenon in which an electrical conductivity is sharply increased by doping halogen elements into polyacetylene and a (CH)x film. Since the polymer such as polyacetylene is comprised of a chain of carbon atoms with alternating single and double bonds between them, π-electrons can be somewhat freely moved. Thus, it is called a “π-conjugated polymer”. Further, if such a polymer is chemically or electrochemically doped, its electrical conductivity can be regulated in a range of from a conductivity of an insulator to a conductivity of a metal. Thus, it is also called a “conducting polymer” or a “synthetic metal”. The conducting polymers have been widely applied not only to the field of chemistry or physics but also to various industry fields due to their characteristics of being pliable and light like plastics.
A Circulating Tumor Cell (CTC) refers to a rare cancer cell that is present in the blood and circulates in the body and plays an important role in tumor metastasis. Therefore, detecting circulating tumor cells remains for a long time as an unsolved problem for diagnosing and treating a cancer. According to the current anticancer treatments, most of patients are uniformly administered with anticancer drugs without checking presence or absence of such CTCs or DTCs (Disseminated Tumor Cells). It is necessary to selectively administer anticancer drugs depending on presence or absence of CTCs by detecting and analyzing the CTCs, or it is necessary to improve efficacy of drugs through personalized administration of drugs depending on molecular characteristics of CTCs.
Circulating tumor cells are known as a factor involved in cancer metastasis and cancer recurrence, and in particular, it is suggested that the circulating tumor cells are likely to include cancer stem cells which is one of the most important subjects of recent cancer research. Therefore, through analysis of circulating tumor cells, a possibility of new cancer prognosis prediction which cannot be obtained by traditional biopsies and a possibility of developing a patient-personalized treatment based it are expected.
However, such circulating tumor cells are very small in quantity within the blood and the cells are weak, and, thus, it is very difficult to detect and quantify them. Therefore, a highly sensitive diagnosis method capable of detecting circulating tumor cells, cancer cells, or cancer stem cells present in the body of a patient is still needed, and a method for efficiently isolating circulating tumor cells contained in a biological sample and an apparatus related thereto are still demanded.
In recent decades, significant efforts have been directed toward the development of novel strategies for acquiring, sorting, and characterizing desired pure cells from complex cell mixtures. Cell isolation and detailed analysis of purified cells is essential for research in a variety of fields such as fundamental biology and for the development of new clinical diagnostics and therapeutic modalities.
Isolation of rare cells such as cancer stem cells and circulating tumor cells (CTCs) from various sources is at great needs because rare types of cancer cells are critical for unraveling mechanisms that are associated with unrestricted cancer development and progression. In particular, because circulating tumor cells play an important role in the metastatic spread of cancer, detection of the circulating tumor cells could have an impact on establishing a theory of metastasis, which consequently introduces the possibility of point-of-care (POC).
Approaches that rely primarily on antigen-antibody affinity by recognizing biomarkers found on target cell membranes with high affinity and specificity have been developed. These include immune-magnetic beads, and micro- and nano-structured surfaces. Compared with traditional bench-top methods such as flow cytometers, the CellSearch system, isolation by size of epithelial tumor cells, current platform-based technologies have demonstrated improved cell recovery and purity and enhanced enrichment of target cells from blood samples.
However, although recent findings have typically focused on enhancing capture yield and sensitivity, techniques for demonstrating the feasibility of non-destructive release of captured cells and subsequent characterization of retrieval cells have not been actively developed.